Formulated feed for shrimp and prawn mass culture and feed ingredients.
Formulated feed for shrimp and prawn mass culture is a very complex mixture of numerous ingredients from different sources specifically addressed to supply the nutrients and energy shrimp and prawn need for best growth. (FAO: www.fao.org/fishery). A complete feed is a formulated pellet that provides all required nutrients in the proper proportions necessary for rapid weight gain, high feed efficiency and necessary for shrimp and prawn health and quality.
Cholesterol, and the fatty acids eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), linoleic acid (LA), and alpha-linolenic acid (ALA) are among the several essential nutrients which cannot be synthesized by shrimp or prawn, so a dietary source is essential.
Cholesteryl esters of normal fatty acids are also useful to this effect as well. Shin-ichi Teshima et al. have shown that the absorptions of free cholesterol and cholesterol esterified with normal fatty acids in a prawn were very similar (Bulletin of the Japanese Society of Scientific Fisheries 49(6) 963-966 (1983)).
Typically, fish oils incorporated into the formulated pellet at 2 to 3 percent, provide the essential fatty acids EPA and DHA, meanwhile vegetable oils like soybean oil and linseed oil provide the essential fatty acids LA and ALA. Dietary requirements of EPA and DHA for shrimp and prawn range from 0.5 to 1.0 percent in the feed. The total lipid content of the formulated pellet should be in the range of 6 to 9%.
Fish oil also contains, on the average, about 1% of total (free and esterified) cholesterol but this does not suffice alone to satisfy the cholesterol requirements of shrimp or prawn, because as mentioned above, fish oil which is included typically at 2 to 3% in the feed would contribute at most only 0.02-0.03% of cholesterol in the diet instead of 0.5 to 1.0%, which is the range of the dietary requirement of cholesterol for shrimp and prawn.
GB 489623 discloses a process for obtaining cholesterol from marine animal oils by subjecting the oil to fractionation through multiple sequential vacuum distillations at different temperature and pressure, wherein one or more of the distillate fractions comprise cholesterol, both free and esterified. Such fractions comprising cholesterol, if desired, may be further purified by methods such as saponification followed by extraction of non-saponifiable matter with a water immiscible solvent, concentration and crystallization.
There are several disadvantages of the process disclosed by GB 489623. At present, fish oil is a valuable commodity due to its content of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid. Multiple distillations of fish oil increase the trans fatty acid content of the oil, and promote polymerization of unsaturated fatty acid, which in turn decrease the content of EPA and DHA. Multiple distillations also render the fish oil unsuitable for human or animal consumption.
On the other hand, present day fish oils contain a great variety of toxic and/or harmful anthropogenic contaminants like polychlorinated biphenyls (PCB), dichlorodiphenyltrichloroethane (DDT) and its metabolites, dibenzo-dioxins (PCDDs), and dibenzo-furans (PCDFs), poly-aromatic hydrocarbons (PAH), pesticides and their degradation products, also known as persistent organic pollutants or POP's, which are resistant to environmental degradation and thus bio-accumulate. Therefore, the distillate fractions comprising cholesterol of the process of GB 489623 will comprise as well one or more of such contaminants and the content of such contaminants in the distillate fractions will be even higher than in the fish oil. This fact, though evident, can be found in the prior art.
U.S. Pat. No. 7,678,930 discloses a process for obtaining a cholesterol-reduced fish oil by vacuum stripping the oil. The distillate is therefore a cholesterol containing composition containing some free EPA and DHA as well. All the fish oil contaminants are concentrated in the distillate or cholesterol containing composition of the process of U.S. Pat. No. 7,678,930.
This is evident from the prior art because U.S. Pat. No. 7,718,698 discloses a process for decreasing the amount of environmental pollutants in fish oil, also by vacuum stripping the oil. U.S. Pat. No. 7,678,930 and U.S. Pat. No. 7,718,698 disclose similar processes. Therefore, under conditions of vacuum distillation where environmental pollutants are removed, cholesterol is removed as well and vice versa. The distillate of the process of U.S. Pat. No. 7,678,930 has a level of toxic and/or harmful anthropogenic contaminants higher than the fish oil and its cholesterol content is no greater than 10%, therefore it is unsuitable as a source of cholesterol in formulated shrimp and prawn feed because it would itself satisfy the total lipid requirements in the feed, leaving no room to further addition of the other two essential fatty acids LA and ALA containing lipids, and would also lead to a feed having contaminants above the maximum permissible limits.
An objective of the present invention is to obtain from fish oil comprising over 2% of free fatty acids, a composition comprising at least 20% of cholesterol and at least 15% of polyunsaturated fatty acids comprising eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), or obtaining a composition comprising at least 50% of cholesteryl esters, the cholesteryl esters comprising at least 20% of cholesteryl esters of eicosapentaenoic acid and docosahexaenoic acid, wherein such compositions may be utilized as feed ingredient in animal feed, such as formulated shrimp and prawn feed, so as to provide the required amount of cholesterol and the essential polyunsaturated fatty acids eicosapentaenoic acid or docosahexaenoic without the need of including fish oil or any additional source of cholesterol in the formulation. In at least one embodiment, the disclosed residual or processed fish oil is a high-quality fish oil suitable for animal or human consumption or for the elaboration of EPA and DHA concentrates.